Phosphorus (P) is
an essential nutrient for crop production, and
animal manures are rich in P. When using animal manures as alternatives
to synthetic fertilizers, it is important to know the kinetics of
P release from different animal manures and the forms, amounts, and
dynamics of P in manure-treated soils. We chose four types of manure,
viz., pig manure (PM), chicken manure (CM), dairy manure (DM), and
commercial organic compost (OM), and evaluated the P release rate
and availability in water solution and flooded/upland paddy soils.
The WEP/total P (TP) and the water-extractable P (WEP) concentrations
are highest for OM with the order: OM > PM > CM > DM. An
increase
in soil Olsen-P concentration was observed for the addition of manure
with a varying application rate of P from low to moderate to high.
The release capacity of Olsen-P in flooded conditions was higher than
that in upland conditions. Under the flooded soil, PM and OM have
faster release rates than CM and OM in the upland soil. Moreover,
PM significantly increased available P by 29% in the flooded paddy
soil while moderately inorganic P increased by 17% in the upland paddy
soil. Olsen-P has a significant linear relationship with available
P (Resin-P + NaHCO3-Pi; R2 =
0.104; P < 0.01) and moderately inorganic P (NaOH-Pi
+ HCl-P; R2 = 0.286; P < 0.01). The structural equation model showed that the organic
input was beneficial to the conversion of moderately inorganic P to
available P. Our results indicate that PM amendment promotes the release
of available P in paddy soil.